1. Field of the Invention
The present invention pertains to a support for a rotary machine tool and more specifically to a support column including various reinforcement ribs extending at an angle to the vertical to maximize the twisting and bending rigidity of the column while minimizing its weight.
2. Discussion of the Prior Art
Rotary machine tools which are mounted for linear movement between an operating position and a non-operating position are known in the art. In such machine tool arrangements, the machine tool itself is secured to a support column which is movable between these positions. Such machine tools generally include a motor, such an electric motor, and a working element which projects outwardly from the column support in the direction of movement. Such working elements generally comprise a rotating spindle head to which various tools, such as cutters and grinders, are detachably secured. These working elements engage a workpiece when the column support is moved to its operating position.
In recent years, it has become desirable to increase the operating speed of such machines while still maintaining or even increasing the machining accuracy. In the prior art, it has been found that raising the rotating speed of the spindle head causes known support columns to vibrate thereby decreasing the machining accuracy. Therefore, in order to increase the machining process speed while maintaining the machining accuracy, it is necessary to increase the rigidity of the support column. If the rigidity of the support column is made too low, the column is apt to vibrate by the reaction force from the machine tool which reduces machining accuracy as discussed above. In addition, while increasing the rigidity of the column is a main concern, it is also important to minimize the increase in the weight of the column since the column is required to move during operation.
Prior art arrangements have increased the rigidity of such support columns in basically two manners. First, it has been proposed to increase the thickness of the column itself. Unfortunately, although this solves the rigidity problem, the weight of the support column is substantially increased which, as stated above, is undesirable. In another known solution, both horizontal and vertical reinforcement ribs have been formed on the inside surface of the support column. These ribs intersect each other at right angles to form a lattice work. With this proposed solution, it has been found that numerous closely spaced, intersecting ribs must be provided in order to solve the rigidity problem. This prior art rib design again has been found to disadvantageously increase the weight of the column.
Therefore, it can be seen that prior art solutions to the present problem have resulted in support column weight increases which result in an increase in the column inertia mass and results in a drop in the transfer speed of the column between its operating positions. This reduction and transfer speed reduces production efficiency of the machine tool. Therefore, there exists a need in the art for a reinforced support column for a machine tool which will improve the column rigidity while minimizing its weight increase to therefore increase machining accuracy while maintaining a high machining process speed.